1. Field of Invention
The invention relates to a light-splitting device and, in particular, to a light-splitting device, which is used in a projection system.
2. Related Art
Currently, image projection systems have become popular items in the optoelectronic industry owing to multiple requirements of a system having large display area, small dimension, and thin, light composition.
With reference to FIG. 1, in a projector system 1, a light source 11 emits light beams, and then the light beams are collimated and integrated by a lens 12. Then, the light beams pass through a filter element 131 of a light-splitting device 13 and a light pipe 14 sequentially. Herein, the filter element 131 is a color filter has green, red and blue sections. The light beams are then projected onto a digital micro-mirror device (DMD) 16 by a reflector 15. Then, the light beams may be projected by a projection lens 17 to form an image on a screen 18. Generally, the temperature of the light source 11 in the projection system 1 is always high to 150° C. to 200° C., so the temperature of the system is also high. A fan 19 is near to the light source 11 in order to decrease the temperature of the light source 11. Herein, the fan 19 has a plurality of blades 191 and a motor 192. The motor 192 drives the blades 191 to rotate, and the rotation of the blades 191 produce airflow, so that heat is transferred away from the projection system 1.
Referring to FIG. 1 and FIG. 2, the light-splitting device 13 mainly includes the filter element 13 and a motor 132. Herein, the motor 132 has a shaft housing 1321 and a motor body 1322. The shaft housing 1321 is disposed on one side of the motor body 1322, and a central axis passes through the shaft housing 1321. Moreover, the light-splitting device 13 further includes a fixing element 1323 and a cable (not shown). The fixing element 1323 is used for fixing the light-splitting device 13 in the projection system 1. The cable connects with a driver, which drives the motor body 1322 to rotate. The motor body 1322 is rotatable around the central axis. Herein, the motor body 1322 is mainly composed of a shell (not shown), a magnetic ring (not shown), a laminated steel stack (not shown) and a coil (not shown). When the coil is powered on, the laminated steel stack produces a magnetic force and a magnetic field. Controlling the positive/negative property and the intensity of the flowing current may change the magnetic field in sequence, or produce a rotating magnetic field, to interact with the magnetic ring and thus cause the magnetic ring to rotate. The filter element 131 is fixed on the shaft housing 1321 of the motor 132 by an adhesive, and the motor 132 drives the filter element 131 to rotate around the central axis for filtering the light beams. In the current industry, the filter element 131 may be a ring-shaped filter composed of different color sections in order to dispose on the shaft housing 1321.
As mentioned above, in the conventional light-splitting device 13, the motor 132 drives the rotation of the filter element 131 for splitting the light beams. However, the high temperature of the projection system 1 may shorten the lifetime of the motor 132. The filter element 131 is fixed on the shaft housing 1321 of the motor 132 by the adhesive. Hence, even only the motor 132 or the filter element 131 is damaged, the light-splitting device 13 is unusable. Because of the above reason, the production cost would be increased.
It is therefore an important subjective of the invention to provide a light-splitting device, which can decrease the production cost and can solve the problem which is described above.